Involvement of D-Aspartate N-Methyl-D-Aspartate in Alzhelmer's Disease, Learning and Memory. Free D-aspartate (D-Asp) is an endogenous amino acid that occurs in nervous and endocrine tissues of a variety of animal phyla from mollusks to mammals, including humans. We have discovered that N-methyI-D-aspartate (NMDA) (the methylated form of D-Asp) is also present as an endogenous amino acid in rat neuroendocrine tissues and is biosynthesized in vivo and in vitro from D-Asp as its natural precursor (D'Aniello, Fisher et al., FASEB J. 2000 and Endocrinology 2000). NMDA receptors in the brain are presumed to be involved in learning, memory, synaptic potentiation, and synaptic depression. A loss of NMDA receptors has been associated with a variety of neurological disorders such as Alzheimer's disease. Since the last competitive renewal in 1998, we have observed that: 1) D-Asp and NMDA possess neurotransmitter activity and biological activity in the release and synthesis of GnRH from the hypothalamus and LH, PRL, and GH from the pituitary, and that NMDA is biosynthesized from D-Asp (D'Aniello, Fisher et al., FASEB J. 2000 and Endocrinology 2000). 2) D-Asp levels are reduced in Alzheimer brain compared to normal brain (Fisher et al., 1991; D'Aniello et al., 1998). 3) If animals are subjected to training exercises for learning and memory (water maze for rat; water pick system for the sea slug Aplysia) the concentrations of D-Asp and NMDA are increased in the rat brain and in the cerebral and abdominal ganglia of Aplysia (unpublished results). Based on these preliminary data, we hypothesize that D-Asp and NMDA are involved in learning and memory xocesses and that the reduction of endogenous D-Asp we find in cortical regions of Alzheimer brain could contribute to the memory loss associated with Alzheimer's disease, due to reduced NMDA biosynthesis from D-Asp. Therefore, the specific aims of this renewal application are: 1. To determine the concentrations of D-Asp and NMDA in various regions of Alzheimer and normal brain in order to know in which areas of the brain and in which type of neurons D-Asp and NMDA occur and to know if there really is a reduction of these amino acids in Alzheimer brains. 2. To determine if D-Asp and NMDA have a role in learning and memory using Aplysia and rats as animal models that will be subjected to exercises to stimulate learning and memory (water pick for Aplysia and water maze for rat) and then analyzed for D-Asp and NMDA concentrations in their nervous systems, thus indicating that these amino acids could be involved in the memory loss associated with neurological diseases. 3. To develop a more sensitive and accurate chromatographic method for direct determination of NMDA in biological tissues.